CN111224576A - High-low voltage composite pulse power supply based on Boost and Buck parallel connection - Google Patents
High-low voltage composite pulse power supply based on Boost and Buck parallel connection Download PDFInfo
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Abstract
The invention discloses a high-low voltage composite pulse power supply based on Boost and Buck parallel connection, which comprises a direct current input power supply, a high-voltage breakdown circuit, a low-voltage discharge circuit, a gap current detection circuit, a gap voltage detection circuit, a drive circuit and an FPGA controller, wherein the high-voltage breakdown circuit and the low-voltage discharge circuit form a pulse power supply main circuit, a composite circuit topology that a Boost circuit is connected with a plurality of synchronous rectification Buck circuits which are connected in parallel in a staggered mode is adopted, and the low-voltage discharge circuit is controlled in a current closed loop mode; the high-voltage breakdown loop adopts voltage closed-loop control; and the flexible switching between the high-voltage breakdown circuit and the low-voltage discharge circuit is completed through the judgment of the gap voltage. The invention improves the energy utilization rate of the pulse power supply, reduces output current ripples, and realizes that the breakdown high voltage can be adjusted and the discharge current waveform can be controlled.
Description
Technical Field
The invention relates to an electric spark forming processing pulse power supply, in particular to a high-low voltage composite pulse power supply based on Boost and Buck parallel connection.
Background
The electric spark forming processing is commonly used for processing a cavity in the production of a die, and the electrolyte adopts spark oil which has high insulativity and needs to apply high voltage for gap breakdown. Along with the increase of the processing depth, the electric spark forming machine tool has poor chip removal, so that the discharge condition is easy to deteriorate, and the abnormal discharge phenomenon becomes more. The magnitude of the distance between the tool electrode and the workpiece electrode is regulated by the voltage across the gap, subject to the current average voltage method of servo tracking. At present, a resistance type pulse power supply is mainly adopted as a pulse power supply for electric spark forming machining, and high voltage for gap breakdown is provided through a transformer and cannot be flexibly adjusted; the discharge energy can be controlled only by adjusting the size of the discharge resistor and the switching frequency, and the defects of low electric energy utilization rate, poor current waveform controllability and the like exist.
Disclosure of Invention
The invention aims to provide a high-low voltage composite pulse power supply based on Boost and Buck parallel connection.
The technical solution for realizing the purpose of the invention is as follows: a high-low voltage composite pulse power supply based on Boost and Buck parallel connection comprises a direct current input power supply, a high-voltage breakdown circuit, a low-voltage discharge circuit, a gap current detection circuit, a gap voltage detection circuit, a drive circuit and an FPGA controller, wherein the high-voltage breakdown circuit and the low-voltage discharge circuit form a pulse power supply main circuit, and a composite circuit topology that a Boost circuit is connected in parallel with a plurality of synchronous rectification Buck circuits which are alternately connected in parallel is adopted; the direct-current power supply is used for supplying power to the high-voltage breakdown loop and the low-voltage discharge loop; the high-voltage breakdown loop is used for providing high voltage required by gap breakdown; the low-voltage discharge loop is used for providing discharge energy; the voltage detection circuit and the current detection circuit are used for sampling the gap voltage and the gap discharge current; the FPGA controller generates a plurality of paths of PWM signals according to the voltage and current sampling signals; the driving circuit is used for filtering and amplifying the PWM signal and controlling the on and off of the switching tubes in the high-voltage breakdown circuit and the low-voltage discharge circuit.
The pulse power supply main circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube, a deionization switch tube, a low-voltage discharge circuit switch tube, a high-voltage breakdown circuit switch tube, a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a first capacitor, a second capacitor, a first output diode, a second output diode, a third output diode, a fourth output diode, a fifth diode and a feedback diode, wherein the first switch tube, the second switch tube, the first output diode and the first inductor form a first path of synchronous rectification Buck circuit; the third switching tube, the fourth switching tube, the second output diode and the second inductor form a second path of synchronous rectification Buck circuit; a third synchronous rectification Buck circuit is formed by a fifth switching tube, a sixth switching tube, a third output diode and a third inductor; a seventh switching tube, an eighth switching tube, a fourth output diode and a fourth inductor form a fourth synchronous rectification Buck circuit; a ninth switching tube, a fifth diode, a fifth inductor and a second capacitor form a Boost circuit; one end of an upper tube of the four-path synchronous rectification Buck circuit is connected to the positive electrode of the input direct-current power supply, and the other end of the upper tube is respectively connected with the first inductor, the second inductor, the third inductor and the fourth inductor in series; one end of a lower tube of the four-path synchronous rectification Buck circuit is respectively connected to a series point between the first inductor, the second inductor, the third inductor, the fourth inductor and the upper tube, and the other end of the lower tube is connected with the negative pole of the input direct-current power supply, namely the lower tube is grounded; one end of a first inductor, a second inductor, a third inductor and a fourth inductor in the four-path synchronous rectification Buck circuit is connected to a common point of an upper tube and a lower tube, and the other end of the first inductor, the second inductor, the third inductor and the fourth inductor is connected with the anode of an output diode; the cathodes of output diodes in the four paths of synchronous rectification Buck circuits are connected together and connected to one end of a low-voltage discharge circuit switching tube, and the other end of the low-voltage discharge circuit switching tube is connected to the anode of the gap; the Boost circuit is connected with the four-way synchronous rectification Buck circuit in parallel, namely one end of the fifth inductor is connected with the anode of the input direct-current power supply, and the other end of the fifth inductor is connected with the anode of the fifth diode; the negative electrode of the fifth diode is connected with a high-voltage breakdown circuit switching tube; one end of the ninth switching tube is connected with a common point between the fifth inductor and the fifth diode, and the other end of the ninth switching tube is connected with the negative pole of the input direct-current power supply, namely the ninth switching tube is grounded; one end of the second capacitor is connected to a common point between the fifth diode and the switching tube of the high-voltage breakdown circuit, and the other end of the second capacitor is connected to the negative pole of the input direct-current power supply, namely the negative pole is grounded; the first capacitor is connected with the direct current input power supply in parallel; the cathode of the feedback diode is connected with the anode of the direct current power supply, and the anode of the feedback diode is connected with the cathode of the first output diode; the two ends of the gap are also connected with a deionization switch tube in parallel; the other end of the gap is connected to the negative pole of the input direct current power supply.
The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, the deionization switch tube, the low-voltage discharge circuit switch tube and the high-voltage breakdown circuit switch tube adopt metal-oxide semiconductor field effect transistors.
The first inductor, the second inductor, the third inductor, the fourth inductor and the fifth inductor are independent inductors, and the magnetic core is made of a sintered magnetic metal oxide made of an iron oxide mixture and made of PC 40.
The first output diode, the second output diode, the third output diode, the fourth output diode, the fifth diode and the feedback diode are Schottky diodes.
The gap voltage detection circuit selects a resistance voltage division circuit.
The gap current detection circuit selects a current hall sensor.
The FPGA controller selects an AX301 series development board.
The driving circuit adopts a driving chip with isolated high-side and low-side dual-output.
The processing control method of the power supply comprises the following steps:
the method comprises the following steps: in the breakdown delay stage, the FPGA controller controls the switching tube of the low-voltage discharge circuit to be switched off, the switching tube of the high-voltage breakdown circuit to be switched on, and the deionization switch tube to be switched off; the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube, the sixth switching tube, the seventh switching tube and the eighth switching tube are turned off; at the moment, a Boost circuit consisting of a ninth switching tube, a fifth diode, a fifth inductor and a second capacitor provides high voltage for the gap, and the FPGA controller outputs a PWM signal to control the duty ratio of the ninth switching tube according to the processing environment and an error signal of gap sampling voltage and a voltage set value, so that the high voltage applied to two ends of the gap is adjusted, and a stable discharge channel is formed;
step two: when the gap is broken down, the gap voltage is reduced to a maintaining voltage from the original open-circuit voltage, the FPGA controller outputs a plurality of paths of PWM signals to control the conduction of the low-voltage discharge switching tube, the switching tube of the high-voltage breakdown circuit is switched off, and the switching from the high-voltage breakdown circuit to the low-voltage discharge circuit is completed;
step three: after the high-voltage breakdown circuit and the low-voltage discharge circuit are switched, the low-voltage discharge circuit starts to provide discharge energy required by machining for the gap, the FPGA controller outputs a plurality of paths of PWM signals according to error signals of gap sampling current and current reference values to control four paths of synchronous rectification Buck circuits to work in a staggered mode, the phase difference of the PWM signals between two adjacent paths is equal to one fourth of the switching period, a certain dead time is reserved for driving signals between upper and lower tubes of the single-path synchronous rectification Buck circuit, and then the continuous discharge machining stage is started;
step four: when the discharge duration reaches a set value, the FPGA controller outputs a plurality of paths of PWM signals to control the switching tube of the low-voltage discharge circuit to be switched off, the switching tube of the high-voltage breakdown circuit is switched off, the deionization switching tube is switched off, the first switching tube, the third switching tube, the fifth switching tube and the seventh switching tube are switched off, the second switching tube, the fourth switching tube, the sixth switching tube and the eighth switching tube are switched on, the ninth switching tube is switched off, energy in the first inductor, the second inductor, the third inductor, the fourth inductor and the fifth inductor is fed back to the input direct-current power supply through the feedback diodes, and at the moment, the discharge tailing stage is started.
Step five: after the gap current is reduced to zero, the FPGA controller outputs a plurality of paths of PWM signals to control the deionization switch tube to be switched on, other switch tubes are switched off, the voltage at two ends of the gap is reduced to zero, and the deionization device enters a deionization stage and prepares for discharging in the next period;
step six: and repeating the five steps to realize the cycle of the processing period.
Compared with the prior art, the invention has the following remarkable advantages: 1) the electric spark machining stability and machining efficiency are improved by adopting a power electronic high-low voltage composite structure; 2) the low-voltage discharge loop adopts a topological structure in staggered parallel connection, so that power expansion is facilitated, switching frequency is equivalently improved, output current ripples are effectively reduced, and the volume of a magnetic element is reduced; 3) the high-voltage breakdown circuit adopts voltage closed-loop control to realize continuous adjustable output high voltage, and the low-voltage discharge circuit adopts current closed-loop control to realize flexible and variable output current waveform according to reference current, so that discharge energy is controllable, and the requirements of different processing modes are met; 4) the switching between the high-voltage breakdown circuit and the low-voltage discharge circuit is carried out by adopting gap voltage judgment, so that the flexibility and the reliability of the switching of the high-voltage circuit and the low-voltage circuit are improved.
Drawings
Fig. 1 is a block diagram of a high-low voltage composite pulse power supply system based on Boost and Buck parallel connection.
Fig. 2 is a schematic topology diagram of a high-low voltage composite pulse power supply based on the parallel connection of Boost and Buck.
Fig. 3 is a schematic diagram of a single-path current closed-loop control adopted by the low-voltage discharge circuit in the invention.
Fig. 4 is a flowchart of the switching control procedure of the high-low voltage circuit according to the present invention.
Fig. 5 is a schematic diagram of a typical discharge waveform of a high-low voltage composite type pulse power supply topology based on the parallel connection of Boost and Buck.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings.
As shown in fig. 1, the high-low voltage composite pulse power supply based on the parallel connection of the Boost circuit and the Buck circuit comprises a direct current input power supply, a high-voltage breakdown circuit, a low-voltage discharge circuit, a gap current detection circuit, a gap voltage detection circuit, a drive circuit and an FPGA controller, wherein the high-voltage breakdown circuit and the low-voltage discharge circuit form a pulse power supply main circuit, and a composite circuit topology in which the Boost circuit is connected in parallel with a plurality of synchronous rectification Buck circuits in a staggered parallel connection mode is adopted; the direct-current power supply is used for supplying power to the high-voltage breakdown loop and the low-voltage discharge loop; the high-voltage breakdown loop is used for providing high voltage required by gap breakdown; the low-voltage discharge loop is used for providing discharge energy; the voltage detection circuit and the current detection circuit are used for sampling the gap voltage and the gap discharge current; the FPGA controller generates a plurality of paths of PWM signals according to the voltage and current sampling signals; the driving circuit is used for filtering and amplifying the PWM signal and controlling the on and off of the switching tubes in the high-voltage breakdown circuit and the low-voltage discharge circuit.
As shown in fig. 2, the main circuit of the pulse power supply includes a first switch tube Q1A second switch tube Q2And a third switching tube Q3And a fourth switching tube Q4The fifth switch tube Q5And a sixth switching tube Q6Seventh switch tube Q7The eighth switch tube Q8And a ninth switching tube Q9Deionization switch tube QoffSwitching tube Q of low-voltage discharge circuitLSwitching tube Q of high-voltage breakdown circuitHA first inductor L1A second inductor L2A third inductor L3A fourth inductor L4A fifth inductor L5A first capacitor CinA second capacitor CoA first output diode D1A second output diode D2A third output diode D3A fourth output diode D4A fifth diode D5And a feedback diode DbackWherein the first switch tube Q1A second switch tube Q2A first output diode D1A first inductor L1Forming a first path of synchronous rectification Buck circuit; third switch tube Q3And a fourth switching tube Q4A second output diode D2A second inductor L2Forming a second path of synchronous rectification Buck circuit; fifth switch tube Q5And a sixth switching tube Q6A third output diode D3A third inductor L3Forming a third synchronous rectification Buck circuit; seventh switch tube Q7The eighth switch tube Q8A fourth output diode D4A fourth inductor L4Forming a fourth path of synchronous rectification Buck circuit; ninth switch tube Q9A fifth diode D5A fifth inductor L5And a second capacitor CoForming a Boost circuit; one end of an upper tube of the four-way synchronous rectification Buck circuit is connected to the positive electrode of the input direct-current power supply, and the other end of the upper tube is respectively connected with the first inductor L1A second inductor L2A third inductor L3A fourth inductor L4Are connected in series; one end of a lower tube of the four-way synchronous rectification Buck circuit is respectively connected to a first inductor L1A second inductor L2A third inductor L3A fourth inductor L4The other end of the series point between the upper tube and the lower tube is connected with the negative pole of the input direct current power supply, namely the input direct current power supply is grounded; first inductor L in four-way synchronous rectification Buck circuit1A second inductor L2A third inductor L3A fourth inductor L4One end of the output diode is connected to the common point of the upper tube and the lower tube, and the other end of the output diode is connected with the anode of the output diode; the cathodes of output diodes in the four-way synchronous rectification Buck circuit are connected together and connected to a switching tube Q of the low-voltage discharge circuitLOne end of (1), a low-voltage discharge circuit switching tube QLThe other end of the first end is connected to the positive pole of the gap; the Boost circuit is connected with the four-way synchronous rectification Buck circuit in parallel, namely a fifth inductor L5One end of the first diode is connected with the anode of the input direct current power supply, and the other end of the first diode is connected with the fifth diode D5The positive electrode of (1); fifth diode D5Negative electrode of the switching tube Q is connected with a high-voltage breakdown circuitH(ii) a Ninth switch tube Q9Is connected with a fifth inductor L5And a fifth diode D5The other end of the common point is connected with the cathode of the input direct current power supply, namely the common point is grounded; second capacitor CoIs connected to a fifth diode D5Switching tube Q connected with high-voltage breakdown circuitHThe other end of the common point is connected with the cathode of the input direct current power supply, namely the common point is grounded; a first capacitor CinIs connected with a direct current input power supply in parallel; feedback diode DbackIs connected with the anode of the DC power supply, and the anode of the DC power supply is connected with a first output diode D1Are connected together; the two ends of the gap are also connected with a deionization switch tube Q in paralleloff(ii) a The other end of the gap is connected to the negative pole of the input direct current power supply.
Further, the first switch tube Q1A second switch tube Q2And a third switching tube Q3And a fourth switching tube Q4The fifth switch tube Q5And a sixth switching tube Q6Seventh switch tube Q7The eighth switch tube Q8And a ninth switching tube Q9Deionization switch tube QoffSwitching tube Q of low-voltage discharge circuitLSwitching tube Q of high-voltage breakdown circuitHA metal-oxide semiconductor field effect transistor is used. First switch tube Q in high-low voltage composite pulse power supply1A second switch tube Q2And a third switching tube Q3And a fourth switching tube Q4The fifth switch tube Q5And a sixth switching tube Q6Seventh switch tube Q7The eighth switch tube Q8An N-channel MOSFET from FAIRCHILD, model FCP36N60N, may be selected. Ninth switch tube Q9Deionization switch tube QoffSwitching tube Q of low-voltage discharge circuitLSwitching tube Q of high-voltage breakdown circuitHAn N-channel MOSFET with the model number of IPP60R074C6 and manufactured by Infineon company can be selected, the on-resistance is small, and the switching loss and the on-loss are low.
Further, the first inductor L1A second inductor L2A third inductor L3A fourth inductor L4A fifth inductor L5Selecting independent inductor and magnetic core of different oxygenThe material of the sintered magnetic metal oxide composed of the iron-oxide mixture can be selected from PC 40.
Further, the first output diode D1A second output diode D2A third output diode D3A fourth output diode D4A fifth diode D5And a feedback diode DbackSchottky diodes are used. The first output diode D1A second output diode D2A third output diode D3A fourth output diode D4And a feedback diode DbackA Schottky diode of the type MBR40250TG from ONSemiconductor may be used, and the peak voltage V may be repeated in reverse directionRRMUp to 250V, average forward current IF(AV)Is 40A; fifth diode D5ON Semiconductor corporation, model FFP30S60S schottky diode with peak reverse voltage VRRMUp to 600V, average forward current IF(AV)At 30A, the switching speed is less than 40 ns.
In order to accurately sample the gap current and the gap voltage in real time, a proper current and voltage detection circuit is also needed. The gap current detection circuit selects a current Hall sensor, can select a current detection chip with the model number of ACS733KLATR-65AB-T, and is provided with good linearity and high detection precision. The gap voltage detection circuit adopts a traditional resistance voltage division circuit, and is simple and reliable.
Further, the digital controller selects an FPGA controller with wider industrial control application, and comprehensively considers resources to select a development module AX301 of ALINX company; the corresponding sampling module is an ALINX9226 module matched with an FPGA development board of an AX4010 model by ALINX company.
Furthermore, the driving circuit adopts a high-side and low-side dual-output driving chip with isolation, a gate driving chip with a model of UCC21220 of Texas instruments can be selected, high-side and low-side dual-output driving is achieved, isolation is provided, and interference between a main circuit and a control circuit is reduced.
In conclusion, the high-low voltage composite type pulse power supply topology based on the parallel connection of the Boost and the Buck adopts the high-low voltage composite type topology, so that the stability and the processing efficiency of the electric spark processing are improved; the multi-path staggered parallel topology structure is convenient for power expansion, can equivalently improve the switching frequency, and effectively reduces output current ripples by staggered superposition of multi-path inductive current; the feedback diode can feed back the inductive energy to the input direct current power supply, and the energy utilization rate is improved.
FIG. 3 is a schematic diagram of a single-path current closed-loop control of a four-path interleaved synchronous rectification Buck circuit. By sampling the gap current i in real timedAnd a reference current irefComparing the error values, and passing the compared error values through a compensation circuit AvGenerating a compensation signal veAnd finally, obtaining a final PWM control signal through a PWM modulator. In order to minimize the gap current ripple, sawtooth waves v of PWM modulators in two adjacent synchronous rectification Buck circuitssawThe phases differ by 90. The voltage closed loop uses conventional PI control to obtain the final PWM control signal.
Fig. 4 is a flowchart of the switching control procedure of the high-low voltage circuit according to the present invention. In a complete processing period, the FPGA controller firstly controls the switching tube of the high-voltage breakdown circuit to be conducted, the switching tube of the low-voltage discharge loop is switched off, and at the moment, the high-voltage circuit starts to work to apply high voltage to a gap for gap breakdown; by sampling the gap voltage vdPerforming voltage comparison if the gap voltage is equal to the sustain voltage vdisThe controller FPGA controls the switching tube of the high-voltage breakdown circuit to be switched off, the switching tube of the low-voltage discharge loop is switched on, and at the moment, the low-voltage discharge loop starts to work to provide discharge energy for the gap. And after one discharge period is finished, switching to the next discharge period until the complete discharge process is finished.
Fig. 5 is a typical gap voltage and current waveform diagram for a complete machining cycle of spark forming, which is divided into three phases: breakdown delay period tdelayAnd a discharge stage tonAnd a deionization phase toff. In the breakdown delay stage, the gap is in an insulation state, the gap current is 0, and the gap voltage is equal to the open-circuit voltage vopen(ii) a After the gap is broken down, the discharge stage is entered,the gap voltage is reduced from the original open circuit voltage to the maintaining voltage vdisAt this time, the waveform of the discharge current follows the reference current irefA change in (c); after the discharge is finished, the deionization stage is started, and the gap voltage and the gap current are both reduced to 0. The processing control method of the high-low voltage composite pulse power supply based on the Boost and the Buck in parallel connection comprises the following specific implementation processes:
the method comprises the following steps: in the breakdown delay stage, the FPGA controller controls the switching tube of the low-voltage discharge circuit to be switched off, the switching tube of the high-voltage breakdown circuit to be switched on, and the deionization switch tube to be switched off; the first switching tube, the second switching tube, the third switching tube, the fourth switching tube, the fifth switching tube, the sixth switching tube, the seventh switching tube and the eighth switching tube are turned off; at this time, a Boost circuit composed of the ninth switching tube, the fifth diode, the fifth inductor and the second capacitor provides high voltage for the gap. Under different processing environments, the FPGA controller outputs a PWM signal to control the duty ratio of the ninth switching tube according to an error signal of the gap sampling voltage and a voltage set value, so that the high voltage applied to two ends of the gap is adjusted, and a stable discharge channel is formed;
step two: when the gap is broken down, the gap discharge stage is started, the gap voltage is reduced to a maintaining voltage from the original open-circuit voltage, the FPGA controller outputs a plurality of paths of PWM signals to control the conduction of the low-voltage discharge switching tube, the switching tube of the high-voltage breakdown circuit is switched off, and the switching from the high-voltage breakdown circuit to the low-voltage discharge circuit is completed;
step three: after the switching between the high-voltage breakdown circuit and the low-voltage discharge circuit is completed, the low-voltage discharge circuit starts to provide discharge energy required by machining for the gap. The FPGA controller outputs a plurality of paths of PWM signals according to error signals of the gap sampling current and the current reference value to control four paths of synchronous rectification Buck circuits to work in a staggered mode, the phase difference of the PWM signals between two adjacent paths is equal to one fourth of the switching period, and the ripple of the total output current reaches the minimum. In order to prevent the input short circuit of the low-voltage discharge circuit caused by the rising time and the falling time of the switching tube, a certain dead time is left for the driving signals between the upper tube and the lower tube of the single-path synchronous rectification Buck circuit. At the moment, entering a continuous discharge machining stage, and setting different reference currents to obtain any discharge current waveform so as to meet the requirements of different machining modes of rough machining, medium machining and fine machining;
step four: when the discharge duration time reaches a set value, the FPGA controller outputs a plurality of paths of PWM signals to control the switching tube of the low-voltage discharge circuit to be switched off, the switching tube of the high-voltage breakdown circuit to be switched off, the deionization switching tube to be switched off, the first switching tube, the third switching tube, the fifth switching tube and the seventh switching tube to be switched off, the second switching tube, the fourth switching tube, the sixth switching tube and the eighth switching tube to be switched on, and the ninth switching tube to be switched off. Inductor L1、L2、L3And L4The energy in the power supply is fed back to the input direct current power supply through the feedback diode, so that the energy utilization rate is improved. At this point the discharge tail phase is entered.
Step five: after the gap current is reduced to zero, the FPGA controller outputs a plurality of paths of PWM signals to control the deionization switch tube to be switched on, and other switch tubes are switched off, so that the voltage at two ends of the gap is reduced to zero, and the deionization circuit enters a deionization stage and prepares for discharging in the next period.
Step six: and repeating the five steps to realize the cycle of the processing period.
In conclusion, in a complete machining process, aiming at the load characteristic of electric spark machining, the voltage is sampled according to the gap, and the FPGA controller controls the high-voltage breakdown circuit and the low-voltage discharge circuit to be freely switched; in the breakdown delay stage, according to different processing modes and processing requirements, the high voltage applied to the two ends of the gap can be flexibly adjusted through voltage closed-loop control. In the discharge machining stage, the synchronous rectification Buck circuits which are connected in parallel in a multi-path staggered mode work cooperatively, so that the working frequency of the circuit is equivalently improved, and output current ripples are reduced. By adopting current closed-loop control, any discharge current waveform can be realized by setting reference current, so that the discharge energy can be controlled.
Claims (10)
1. A high-low voltage composite pulse power supply based on Boost and Buck parallel connection is characterized by comprising a direct current input power supply, a high-voltage breakdown circuit, a low-voltage discharge circuit, a gap current detection circuit, a gap voltage detection circuit, a drive circuit and an FPGA controller, wherein the high-voltage breakdown circuit and the low-voltage discharge circuit form a pulse power supply main circuit, and a composite circuit topology that a Boost circuit and a plurality of synchronous rectification Buck circuits which are connected in parallel in a staggered mode are adopted; the direct-current power supply is used for supplying power to the high-voltage breakdown loop and the low-voltage discharge loop; the high-voltage breakdown loop is used for providing high voltage required by gap breakdown; the low-voltage discharge loop is used for providing discharge energy; the voltage detection circuit and the current detection circuit are used for sampling the gap voltage and the gap discharge current; the FPGA controller generates a plurality of paths of PWM signals according to the voltage and current sampling signals; the driving circuit is used for filtering and amplifying the PWM signal and controlling the on and off of the switching tubes in the high-voltage breakdown circuit and the low-voltage discharge circuit.
2. The Boost-Buck parallel-based high-voltage and low-voltage compound type pulse power supply according to claim 1, wherein the pulse power supply main circuit comprises a first switching tube (Q)1) A second switch tube (Q)2) And a third switching tube (Q)3) And a fourth switching tube (Q)4) And a fifth switching tube (Q)5) And a sixth switching tube (Q)6) And a seventh switching tube (Q)7) And an eighth switching tube (Q)8) And a ninth switching tube (Q)9) Deionization switch tube (Q)off) Switching tube (Q) of low-voltage discharge circuitL) Switching tube (Q) of high voltage breakdown circuitH) A first inductor (L)1) A second inductor (L)2) A third inductor (L)3) A fourth inductor (L)4) A fifth inductor (L)5) A first capacitor (C)in) A second capacitor (C)o) A first output diode (D)1) A second output diode (D)2) A third output diode (D)3) And a fourth output diode (D)4) A fifth diode (D)5) And a feedback diode (D)back) Wherein the first switch tube (Q)1) A second switch tube (Q)2) A first output diode (D)1) A first inductor (L)1) Forming a first path of synchronous rectification Buck circuit; third switch tube (Q)3) And a fourth switching tube (Q)4) A second output diode (D)2) A second inductor (L)2) Form the second path of synchronizationA rectifying Buck circuit; fifth switch tube (Q)5) And a sixth switching tube (Q)6) A third output diode (D)3) A third inductor (L)3) Forming a third synchronous rectification Buck circuit; seventh switch tube (Q)7) And an eighth switching tube (Q)8) And a fourth output diode (D)4) A fourth inductor (L)4) Forming a fourth path of synchronous rectification Buck circuit; ninth switch tube (Q)9) A fifth diode (D)5) A fifth inductor (L)5) And a second capacitance (C)o) Forming a Boost circuit; one end of an upper tube of the four-way synchronous rectification Buck circuit is connected to the positive electrode of the input direct-current power supply, and the other end of the upper tube is respectively connected with a first inductor (L)1) A second inductor (L)2) A third inductor (L)3) A fourth inductor (L)4) Are connected in series; one end of a lower tube of the four-way synchronous rectification Buck circuit is respectively connected to a first inductor (L)1) A second inductor (L)2) A third inductor (L)3) A fourth inductor (L)4) The other end of the series point between the upper tube and the lower tube is connected with the negative pole of the input direct current power supply, namely the input direct current power supply is grounded; first inductor (L) in four-way synchronous rectification Buck circuit1) A second inductor (L)2) A third inductor (L)3) A fourth inductor (L)4) One end of the output diode is connected to the common point of the upper tube and the lower tube, and the other end of the output diode is connected with the anode of the output diode; the cathodes of output diodes in the four-way synchronous rectification Buck circuit are connected together and connected to a switching tube (Q) of the low-voltage discharge circuitL) One end of (1), a low-voltage discharge circuit switching tube (Q)L) The other end of the first end is connected to the positive pole of the gap; the Boost circuit is connected with the four-way synchronous rectification Buck circuit in parallel, namely a fifth inductor (L)5) One end of the first diode is connected with the anode of the input direct current power supply, and the other end is connected with a fifth diode (D)5) The positive electrode of (1); fifth diode (D)5) Negative pole of the switching tube (Q) is connected with a high-voltage breakdown circuitH) (ii) a Ninth switch tube (Q)9) Is connected to a fifth inductance (L)5) And a fifth diode (D)5) The other end of the common point is connected with the cathode of the input direct current power supply, namely the common point is grounded; a second capacitance (C)o) Is connected to a fifth diode (D)5) Switching tube (Q) for high voltage breakdown circuitH) In the sense of the common point between them,the other end is connected with the negative electrode of the input direct current power supply, namely the negative electrode is grounded; a first capacitor (C)in) Is connected with a direct current input power supply in parallel; feedback diode (D)back) Is connected with the positive pole of the direct current power supply, and the positive pole of the direct current power supply is connected with the first output diode (D)1) Are connected together; the two ends of the gap are also connected with a deionization switch tube (Q)off) (ii) a The other end of the gap is connected to the negative pole of the input direct current power supply.
3. The Boost-Buck parallel connection-based high-low voltage compound pulse power supply according to claim 2, wherein the first switching tube (Q)1) A second switch tube (Q)2) And a third switching tube (Q)3) And a fourth switching tube (Q)4) And a fifth switching tube (Q)5) And a sixth switching tube (Q)6) And a seventh switching tube (Q)7) And an eighth switching tube (Q)8) And a ninth switching tube (Q)9) Deionization switch tube (Q)off) Switching tube (Q) of low-voltage discharge circuitL) Switching tube (Q) of high voltage breakdown circuitH) A metal-oxide semiconductor field effect transistor is used.
4. The Boost-and-Buck parallel-based high-low voltage composite pulse power supply according to claim 2, wherein the first inductor (L)1) A second inductor (L)2) A third inductor (L)3) A fourth inductor (L)4) A fifth inductor (L)5) The individual inductors were selected and the magnetic core was a sintered magnetic metal oxide consisting of a mixture of iron oxides, the material of which was PC 40.
5. The Boost-and-Buck parallel-based high-low voltage composite pulse power supply according to claim 2, wherein the first output diode (D)1) A second output diode (D)2) A third output diode (D)3) And a fourth output diode (D)4) A fifth diode (D)5) And a feedback diode (D)back) Schottky diodes are used.
6. The Boost and Buck parallel-based high-low voltage composite pulse power supply according to claim 1, wherein the gap voltage detection circuit selects a resistance voltage division circuit.
7. The Boost and Buck parallel-based high-low voltage compound pulse power supply according to claim 1, wherein the gap current detection circuit selects a current hall sensor.
8. The Boost and Buck parallel-based high-low voltage composite pulse power supply according to claim 1, wherein an AX301 series development board is selected as the FPGA controller.
9. The Boost-Buck parallel high-low voltage composite pulse power supply according to claim 1, wherein the driving circuit is a driving chip with isolated high-side and low-side dual output.
10. A process control method based on the power supply of any one of claims 1 to 9, comprising the steps of:
the method comprises the following steps: in the breakdown delay stage, the FPGA controller controls a low-voltage discharge circuit switching tube (Q)L) Switching tube (Q) of turn-off, high voltage breakdown circuitH) Conducting deionization switch tube (Q)off) Turning off; first switch tube (Q)1) A second switch tube (Q)2) And a third switching tube (Q)3) And a fourth switching tube (Q)4) And a fifth switching tube (Q)5) And a sixth switching tube (Q)6) And a seventh switching tube (Q)7) And an eighth switching tube (Q)8) Turning off; at this time, the ninth switch tube (Q)9) A fifth diode (D)5) A fifth inductor (L)5) And a second capacitance (C)o) The composed Boost circuit provides high voltage for the gap, and the FPGA controller samples the voltage and a voltage set value (v) according to the processing environment and the gapopen) The error signal of (2) outputs a PWM signal to control the ninth switching tube (Q)9) So as to regulate the high voltage applied across the gapSmall, form a stable discharge channel;
step two: when the gap breaks down, the discharge stage is entered, and the gap voltage is changed from the original open circuit voltage (v)open) Down to the sustain voltage (v)dis) The FPGA controller outputs multiple PWM signals to control the low-voltage discharge switching tube (Q)L) Switching tube (Q) of conducting, high-voltage breakdown circuitH) Switching off to complete switching from the high-voltage breakdown circuit to the low-voltage discharge circuit;
step three: after the high-voltage breakdown circuit and the low-voltage discharge circuit are switched, the low-voltage discharge circuit starts to provide discharge energy required by machining for the gap, and the FPGA controller samples current (i) according to the gapd) And a current reference value (i)ref) The error signal of the control circuit outputs a plurality of paths of PWM signals to control four paths of synchronous rectification Buck circuits to work in a staggered mode, the phase difference of the PWM signals between two adjacent paths is equal to one fourth of the switching period, a certain dead time is left for driving signals between an upper tube and a lower tube of the single-path synchronous rectification Buck circuit, and the continuous discharge machining stage is started at the moment;
step four: when the discharge duration (pulse width) reaches a set value (t)on) In time, the FPGA controller outputs a plurality of PWM signals to control a low-voltage discharge circuit switching tube (Q)L) Switching tube (Q) of turn-off, high voltage breakdown circuitH) Switch-off, deionization switch tube (Q)off) Off, first switching tube (Q)1) And a third switching tube (Q)3) And a fifth switching tube (Q)5) And a seventh switching tube (Q)7) Off, second switching tube (Q)2) And a fourth switching tube (Q)4) And a sixth switching tube (Q)6) And an eighth switching tube (Q)8) Conducting, ninth switching tube (Q)9) Off, first inductance (L)1) A second inductor (L)2) A third inductor (L)3) A fourth inductor (L)4) A fifth inductor (L)5) Through a feedback diode (D)back) And feeding back the input direct current power supply, and entering a discharge tailing stage.
Step five: after the gap current is reduced to zero, the FPGA controller outputs a plurality of paths of PWM signals to control the deionization switch tube (Q)off) The other switch tubes are turned off to make the two ends of the gap electrically connectedThe voltage drop is zero, and the deionization stage is carried out to prepare for the next period of discharge;
step six: and repeating the five steps to realize the cycle of the processing period.
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